1. Field of the Invention
The present invention relates to a projector and, more particularly, to a projector in which all of optical elements constituting a projection optical system are constituted with reflection mirrors.
2. Description of the Prior Art
As a projector, a liquid crystal projector is widely used as a compact projector in which liquid crystal display elements are used as an image-forming component.
FIG. 1A illustrates an example of a conventional liquid crystal projector and FIG. 1B shows its optical system schematically.
As shown in FIG. 1B, the conventional liquid crystal projector has a casing 23 in which a light source 20 as an illumination source, a liquid crystal display panel 21 and a focusing optical system 22 are housed. The focusing optical system 22 is mounted on an internal side surface of the casing 23.
Light emitted from the light source 20 is incident on the liquid crystal display panel 21 and modulated with an image formed in the liquid crystal display panel 21. The modulated light is expanded by the focusing optical system 22 to reproduce an enlarged image on a screen 24. Incidentally, the liquid crystal display panel 21 used in this example is of the transmission type.
In the conventional liquid crystal projector shown in FIG. 1B, however, projection light is derived out from the focusing optical system 22, which is disposed in an exit portion of the casing 23. The focusing optical system 22 is constructed with a plurality of refractive optical elements such as lenses and fixed suitably in the casing 23 so that an external preciseness of the respective refractive optical elements within the focusing optical system is Maintained. An adjustment for a focal point of the projecting optical system is performed by merely moving a portion of the focusing optical system.
On the other hand, a focusing optical system disclosed in JP H11-125865 A is an eccentric optical system using reflective optical elements. In such focusing optical system, an image quality is degraded due to an arranging error of the respective reflective optical elements, particularly, distance error between the reflective optical elements, and the angle error thereof. It is also difficult to predict stray light within the casing. Accordingly, a monolithic construction in which all of the reflective optical elements constituting the focusing optical system are arranged in one casing is employed.
However, in order to adjust the focus point by a movement of one reflection mirror, it is necessary to mount the reflective optical elements in the casing while maintaining mounting precision. Since it is further necessary to support the reflective optical elements with high mounting precision thereof during the focal point control, the supporting mechanism of the reflective optical elements and the focal point adjustment mechanism becomes complicated, therefore, the resultant projector is expensive.
An object of the present invention is to provide a projector, which does not require any mutual adjustment of reflective optical elements constituting a focusing optical system of the projector after these elements are assembled.
In order to achieve this object, a projector according to the present invention having a projecting optical system for projecting light from image forming elements onto a screen features all of optical elements constituting the projecting optical system being reflective optical elements, respectively. And a position of the whole projecting optical system is adjustable with respect to an image-forming component of the projector by arranging the reflective optical elements on a plate-shaped support member with relative positional relation thereof being fixed and moving the support member.
The reflective optical elements are preferably reflection mirrors, respectively. Furthermore, the present invention features the reflective optical elements being fixed to the plate-shaped support member by inserting the reference pins into the respective reference holes provided on the reflective optical elements and the support member.
Alternatively, the present invention features providing fitting holes in the plate-shaped support member. Each fitting hole has a configuration contoured correspondingly to an outer configuration of a fitting portion of each reflective optical element such that the reflective optical element is fixed onto the plate-shaped support member by fitting the reflective optical elements in the respective fitting holes of the support member.
Alternatively, the present invention features the reflective optical elements being arranged on the support member with the relative positional relation between the reflective optical elements on the support member being fixed, by providing abutment portions each confronted with a fitting portion of each reflective optical element, with which the reflective optical element is fixed onto the plate-shaped support member, in the support member and confronting the fitting portions of the reflective optical system with the respective abutment portions of the support member.
Furthermore, the present invention features a light shield for removing stray light of a light beam from an image-forming element and an iris portion for removing useless light contained in the light beam in the projecting optical system being provided on the plate-shaped support member on which the reflective optical elements are arranged.